Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Strange - counter counts without clock

Something strange happened, and I have no idea for now, what to look for... Below you can see the part of the schematics (testing on DE2-115 board, clk frequency - 10MHz). Very straightforward design...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

looks like you are connecting outputs of counter as feedback to clock the counter. This is complicated design and may oscillate out of control.

Your method falls in the category of asynchronous which is not recommended in FPGAs as the alternative synchronous design is simpler to control.